1. Field of the Invention
The present invention relates to certain substituted aromatic polyimide separation membranes particularly useful for separating gases and the process of using them.
2. Prior Art
U.S. Pat. Nos. 3,822,202 and 3,899,309 disclose aromatic polyimide gas separation membranes in which the molecular structure is such that the molecules in the polymer are unable to pack densely, and, therefore, have high gas permeation rates.
U.S. Pat. No. 4,113,628 and U.K. No. 1,435,151 disclose aromatic polyimide gas separation membranes prepared from polyamide acid membranes.
EPO No. 132,221 and EPO No. 141,781 disclose substituted aromatic polymimides and photochemically crosslinked compositions thereof, but not for use as gas separation membranes.
U.S. Pat. Nos. 4,370,290, 4,460,526, 4,474,662, 4,512,893, U.K. No. 2,098,994, U.K. No. 2,101,137, and U.K. No. 2,102,333 disclose microporous aromatic polyimide membranes and the process from which they are prepared.
U.S. Pat. No. 4,486,376 and U.K. No. 2,104,832 disclose gas separation membranes made from a microporous aromatic polyimide support treated with modifying agents.
U.S. Pat. Nos. 4,378,324, 4,440,643, 4,474,858, 4,485,056, 4,528,004, U.K. No. 2,102,726, U.K. No. 2,104,411 and U.K. No. 2,104,905 disclose gas separation membranes made from a microporous aromatic polyimide support coated with an aromatic polyamide acid or aromatic polyimide.
U.S. Pat. No. 4,378,400 and EPO No. 43,265 disclose aromatic polyimide gas separation membranes in which the molecular structure is such that the molecules in the polymer can pack densely.
U.S. Pat. No. 4,578,166 discloses polymers comprising as the essential component a saturated linear polyester or polyamide and copolymerized therewith benzophenone tetracarboxylic groups which are crosslinked by irradiation.
EPO No. 113,574 discloses gas separation membranes made from aromatic polyetherimides.
EPO No. 143,552 discloses gas separation membranes made from a microporous aromatic polyimide support coated with a crosslinked silicone resin film.
EPO No. 0,125,908 discloses aromatic polyimide reverse osmosis membranes.